SQLAlchemy的数据对象实例能否转为一个简单的对象（切断与数据库会话的联系）

SQLAlchemy

from sqlalchemy import create_engine

from sqlalchemy.orm import sessionmaker

from sqlalchemy.ext.declarative import declarative_base



Base = declarative_base()





class User(Base):

    __tablename__ = 'USER'



    id = Column(Integer, Sequence('USER_SEQ'), primary_key=True, autoincrement=True)

    name = Column(String(30))

    age = Column(Integer)

    status = Column(String(30))





engine = create_engine(str(db_url), encoding=b'utf-8', echo=echo, convert_unicode=True)

Session = sessionmaker(bind=engine)

session = Session()



user = User(name='John', age=30)

session.add(user)

session.commit()

session.close()



print user.name

Traceback (most recent call last):

  File "E:\WorkCopy\test\test.py", line 21, in test_something

    print user.name

  File "C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py", line 237, in __get__

    return self.impl.get(instance_state(instance), dict_)

  File "C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py", line 573, in get

    value = state._load_expired(state, passive)

  File "C:\Python27\lib\site-packages\sqlalchemy\orm\state.py", line 480, in _load_expired

    self.manager.deferred_scalar_loader(self, toload)

  File "C:\Python27\lib\site-packages\sqlalchemy\orm\loading.py", line 610, in load_scalar_attributes

    (state_str(state)))

DetachedInstanceError: Instance is not bound to a Session; attribute refresh operation cannot proceed

SQLAlchemy